Dynamic Response of Adjacent Prestressed Concrete Box Beam Bridge utilizing Reinforced UHPC Shear Keys

Adjacent precast pre-stressed concrete box beam bridges are popular for medium and short spans in North America due to ease and speed of construction and high torsional rigidity. However, longitudinal cracks in the shear keys, which can cause reflective cracks in an overlay or in a composite deck, are one of the most critical issues with these bridges. These cracks can lead to leakage and cause corrosion of the reinforcement, and in severe cases can lead to a reduction or loss of load transfer between beams. Many solutions have been used to eliminate or reduce the cracks in the shear keys. However, some adjacent box beam bridges still exhibit longitudinal cracks. Recently, Ultra High Performance Concrete (UHPC) has been used as a grout material in the connections between prefabricated bridge elements due to the superior mechanical, bonding, and durability properties. In this paper, the dynamic response of the first adjacent precast prestressed concrete box beam bridge in the United States utilizing partial depth reinforced UHPC shear keys was investigated. Instrumentation was installed at different locations, and the bridge behavior was monitored. The dynamic response was compared with the static response. Furthermore, the dynamic amplification factor (DAF) was determined and compared with AASHTO LRFD Design Specification. The results from the moving load showed that the bridge behaved as a unit which emphasize the ability of the new connection to transversally transfer the load. The results also show that the dynamic amplification factor (DAF) from the AASHTO LRFD Design Specification is conservative compared with the measured value.